• Journal of Powder Materials
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• 제12권4호
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• pp.296-302
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• 2005

In order to improve mechanical properties, the hypereutectic Al-20 wt%Si based prealloy powder was prepared by gas atomization process. Microstructure and compressibility of the atomized Al-Si powder were investigated. The average powder size was decreased with increasing the atomization gas pressure. Size of primary Si particles of the as-atomized powder was about $5-8\;\mu{m}$. The as-atomized Al-Si powder such as AMB 2712 and AMB 7775 to increase compressibility and sinterability. Relative density of the mixed powder samples sintered at $600^{\circ}C$ was reached about 96% of a theoretical density.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제14권5호
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• pp.439-448
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• 2004

Magnetic bearing is an attractive device in precision engineering field because of its non-contacting nature and controllability of its dynamic characteristics. This paper provides a method of designing a sliding mode control for an active magnetic hearing(AMB) system which is used to support the elevation axis of a target tracking sight instead of mechanical bearings to eliminate the effect of mechanical friction. In such system, the axis should be levitated and supported within a predetermined air gap while AMB is excited by base motion. Experimental results showed that the sliding mode control is effective in disturbance rejection than conventional PID-control without any additive measurements.

• Proceedings of the KSME Conference
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.548-553
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• 2000

A new design of cylindrical capacitive sensor(CCS) for the displacement measurement of precision active magnetic bearing(AMB) spindle is presented in this paper. This research is motivated by the problem that existing 4-segment CCS is still sensitive to the $3^{rd}$ harmonic component of the geometric errors of a rotor. The procedure of designing new CCS starts from the modeling and error analysis of CCS. The angular size of CCS is set up as a design parameter, and new 8-segment CCS is introduced to possess an arbitrary angular size. The optimum geometry of CCS to minimize the effect of geometric errors is determined through minimum norm approach. Experimental results with test rotors have confirmed the improvement in geometric error suppression.

• Journal of Powder Materials
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• 제9권2호
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• pp.116-123
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• 2002

The characteristics of two commercial 2xxx series Al alloy powders, AMB2712 and 201AB, were evaluated and their compacting and sintering characteristics were discussed in tems of compacting pressure. The particle shapes of both two powder mixtures were irregular and their particle size distributions were broad. The compactibility of AMB2712 was superior to that of 201AB because of better fluidity. The sintered density was higher than the green density at low compacting pressure, however, it was lower than the green density when the samples were compacted at higher pressure due to the selling during sintering. The sintered density was alomost the same as the green density at the "homogeneous deformation" stage. It was observed that pores were created at the triple points due to the rapid diffusion of Cu in Al. Cu in Al.

• The Transactions of the Korean Institute of Electrical Engineers B
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• 제53권2호
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• pp.82-89
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• 2004

In this paper, an active magnetic bearing(AMB) system is designed and controlled using a digital Proportional-Integral-Derivative(PID) control concept. The plant dynamics consisting of actuator and rigid rotor dynamics are described. A digital PID controller with a global control and a local control concept is designed and implemented using digital signal processor. Some experiments are conducted with each global control and local control concept. These include start-up test, impulse test, whirl response, and generator load test. The experimental results and comparison between those of a global control and a local control indicate that the global control of concept has impressive static and dynamic control performance for the prototype considered. From the whirl test, the developed system set can be controlled within about $\pm10\mu\textrm{m}$ gap variation at the rotational speed of 6000rpm and generate the AC power of frequency of $60\textrm{Hz}$, voltage of 100V and current of 0.8$\textit{A}$.

• Journal of the Korean Applied Science and Technology
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• 제38권5호
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• pp.1265-1272
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• 2021

This study was intended to investigate the potential of Astragalus membranaceus ethanol extract(AM) and Astragalus membranaceus bioconversion extract(AMB) as functional cosmetic materials. To confirm the antioxidant effect, polyphenol and flavonoid contents were measured, and a study was conducted on skin cell toxicity and skin cell aging through cell experiments. As a result of the antioxidant experiment, the content of polyphenols and flavonoids increased in a concentration-dependent manner in the effects of polyphenols and flavonoids, and it was confirmed that the ethanol extracts were higher than the bioconversion extracts. It was confirmed that the AM and AMB increased the MMP1 expression inhibitory effect in a concentration-dependent manner in HDF cells. Therefore, this study is considered to be very useful as a functional cosmetic material in terms of antioxidant and skin aging prevention when using AM and AMB as functional cosmetic materials.

• Journal of the Korean Society of Food Science and Nutrition
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• 제40권12호
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• pp.1793-1796
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• 2011

The effects of ethanol extracts from Astragali membranaceus Bunge (AMB) and A. membranaceus Bunge var mongholicus Hisiao (AMBMH) on antioxidant and nitric oxide (NO) production were evaluated. The total polyphenol contents of AMBMH extracts from two, four, and six-year old roots was 45.3, 71.3, and 78.0 mg/g, respectively. These values and those of total flavonoid content were higher than those of AMB extracts. The DPPH radical scavenging activity was the highest in ethanol extracts from four-year old AMBMH roots. The ABTS radical scavenging activity was also higher than those of AMB in ethanol extracts from four- and six-year old AMBMH roots, but not in two-year old roots. The NO production of ethanol extracts from six-year old AMBMH roots was higher than that of two- and four-year old AMBMH roots. However, there is no significant difference in NO production based on the cultivation period of AMB.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2509-2512
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• 2003

The active magnetic bearing(AMB) has statey-state error of the displacement by the external force. This paper presents a PID controller design using LQR method in the active magnetic bearing to compensate for the displacement by the external force.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.771-772
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.701-702
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• 2010